Freak out over coop changes

Ever since my new chicks, now 7 wks old, were released into the coop my 2 yr olds hens have stopped laying in the coop. Everyone gets along pretty well. The chicks insist on using the same roosting bar, even though I put a lower one for them. Only the white leghorn pecks at them, but they curl up with my Silkie, who doesn't seem to mind, at the opposite end of the pole. My hens are now laying under a bush up on a hill in the yard.UUHGG! I tried locking them in the run, but I have one chicken that gets so noisy I can't stand it so I let them out. I have put some fake eggs in their nesting boxes, I don't know what else to do.

My coop is a shed style on the ground 8x6, 8ft tall, front wall is all wire. I have a shelf about 18 inches off the ground with four large nesting boxes. The roost stretches across the whole 8 ft back side. Plenty of room for 7 grown hens and three chicks. My chickens free range from sunrise to sunset, but they have easy access to the coop as the door to the run is always open for food and water. After school lets out, my neighbor is an elementary school, I am going to try keeping them locked in the run for a couple of days. I have two very noisy chickens who complain very loudly if they are not let out of run. I will drag some junk up the hill and stuff it under the bush.